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Commit 352c1d95 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARC: stop using pt_regs->orig_r8 



Historically, pt_regs have had orig_r8, an overloaded container for
  (1) backup copy of r8 (syscall number Trap Exceptions)
  (2) additional system state: (syscall/Exception/Interrupt)

There is no point in keeping (1) since syscall number is never clobbered
in-place, in pt_regs, unlike r0 which duals as first syscall arg as well
as syscall return value and in case of syscall restart, the orig arg0
needs restoring (from orig_r0)  after having been updated in-place with
syscall ret value.

This further paves way to convert (2) to contain ECR itself (rather than
current madeup values)

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 359105bd

arch/arc/include/asm/entry.h

+1 −12
Original line number Diff line number Diff line
@@ -422,18 +422,7 @@ 
 * Save scratch regs for sys calls

 *-------------------------------------------------------------*/

.macro SAVE_ALL_TRAP

	/*

	 * Setup pt_regs->orig_r8.

	 * Encode syscall number (r8) in upper short word of event type (r9)

	 * N.B. #1: This is already endian safe (see ptrace.h)

	 *      #2: Only r9 can be used as scratch as it is already clobbered

	 *          and it's contents are no longer needed by the latter part

	 *          of exception prologue

	 */

	lsl  r9, r8, 16

	or   r9, r9, orig_r8_IS_SCALL



	SAVE_ALL_EXCEPTION  r9

	SAVE_ALL_EXCEPTION  orig_r8_IS_SCALL

.endm



/*--------------------------------------------------------------

arch/arc/include/asm/syscall.h

+2 −3
Original line number Diff line number Diff line
@@ -18,7 +18,7 @@ static inline long 
syscall_get_nr(struct task_struct *task, struct pt_regs *regs)

{

	if (user_mode(regs) && in_syscall(regs))

		return regs->orig_r8;

		return regs->r8;

	else

		return -1;

}
@@ -26,8 +26,7 @@ syscall_get_nr(struct task_struct *task, struct pt_regs *regs) 
static inline void

syscall_rollback(struct task_struct *task, struct pt_regs *regs)

{

	/* XXX: I can't fathom how pt_regs->r8 will be clobbered ? */

	regs->r8 = regs->orig_r8;

	regs->r0 = regs->orig_r0;

}



static inline long

arch/arc/include/uapi/asm/ptrace.h

+1 −1
Original line number Diff line number Diff line
@@ -44,7 +44,7 @@ struct user_regs_struct { 
		long r19, r18, r17, r16, r15, r14, r13;

	} callee;

	long efa;	/* break pt addr, for break points in delay slots */

	long stop_pc;	/* give dbg stop_pc directly after checking orig_r8 */

	long stop_pc;	/* give dbg stop_pc after ensuring brkpt trap */

};

#endif /* !__ASSEMBLY__ */